Control of the Cotton Aphid on Chrysanthemum Under Greenhouse Conditions, Winter 1991

Chrysanthemums were obtained as rooted cuttings and potted in 15 cm pots in a greenhouse at UCR and allowed 8 wk growth (25-30 cm tall) before use. During the growth phase, the plants were exposed to heavy populations of aphids. By 4 wk, all plants were moderately infested with aphids. The terminal portion (3 unexpanded leaves) of each plant was marked with a twist tie and used for aphid counts. Pre- and post-treatment counts were made on the same aphids and their young, if produced. To ensure an equal distribution of aphids/treatment, plants were assigned to treatments in a RCB design on raised greenhouse benches. Six plants/treatment were sprayed at 40 psi to runoff using a hand sprayer. All spray treatments were made weekly for 4 wk. The Merit 0.5%G soil treatment was made only once at the beginning of the trial. Pretreatment counts and treatments were made on the same day (day 0). Post-treatment counts were taken 14 and 28 DAT.